Blast discharge controlling circuit maker



Nov. 7, 1939. G. c NELMS BLAST DISCHARGE CONTROLLING CIRCUIT MAKER Filed Dec. 20, 19s? WSW RN Wm mmwww .N

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Patented Nov. 7, 1939 UNITED smres PATENT OFFHCE MAKE George G. Nelnis, Pittsburgh; Pa., assignor to Portable Lamp and Equipment 00., Pittsburgh, Pa, a corporation of Pennsylvania.

Application December 20,1937, Serial No. 180,859

1 Claim.

The invention relates generally to blasting equipment employed in mining and quarrying, and primarily seeks to provide a reliable, eiricient, compact and inexpensively constructed circuit maker unit by use of which an operative can safely establish an electrical circuit suitablefor discharging individual, remotely placed biast charges.

In present day mining and quarrying, rigid rules and regulations have been laid down for controlling operations in a manner intended to minimize the dangers necessarily present in this hazardous form of employment and to eliminate, if possible, deaths due to carelessness and accident. For example, multiple shooting, that is, the firing of more than one charge at the same time and with the same blasting or control device, has been legislated against. The reason for this is that when a plurality of holes have been drilled and loaded, and all are shot at the same time, the entire face of the material being blasted is brought down. Should one of the charges fail to explode, a miner later striking itwith his pick might set off the charge and cause his death or an even worse mine disaster. 7 For such reasons only single shots are permitted in mines in some localities.

Safety regulations in the mines also prohibit the use of blast controlling devices in which are employed exposed terminals to which conductor lines could be made fast. In the use of such devices it sometimes happens that a charge will fail to go 011, and the operatonwithout disconnecting the conductor lines at the terminals, walks along the lines looking for the break expected to be present therein, and finding and connecting the broken wire ends fires the charge and injures or kills himself in the resultant blast.

The present invention seeks to overcome the dangers referred to, by provision of a compact, sealed and water proof unit containing circuit energizing batteries and having suitable apertures through which bared conductor wire ends may be inserted to make temporary connection with the source of electrical energy for the purpose of firing the blast charge, but which is devoid of any part to which any sustained electrical connection can be made which would enable an operator to make negligent use of the unit as above described.

Another object of the invention is to provide a unit of the character stated in which provision is made for replacing the contained batteries; in

which the unit shell or casing is effectively sealed against tampering; and in which the conductor -formed of wood or any other suitable electricity wire receiving apertures are so shaped as to facilieral views illustrated in the accompanying drawing.

In the drawing:

Figure 1 is a longitudinal sectional View illustrating my improved unit.

Figure 2 is a vertical cross section taken line 2-2 on Figure 1.

Figure 3 is a detail longitudinal section of the removable closure plug and the internally threadedplug receiving end of the unit casing or shell.

Figure 4 is a vertical cross section taken on the line 4-4 on Figure 1.

Figures 5 and 6 are end elevations of the respective ends of the unit. I

Figure 7 is a fragmentary longitudinal section of the removable closure equipped end of the unit on the Figure 8 is an end view of the parts shown in Figure '7, parts being broken away and in section. In the practical development of the invention I provide a cylindrical sleeve shell or casing 5,

non-conducting material, closed at one end, by termination of the sleeve bore or by use of a wooden plug 6 glued and nailed in place as at i,

and provided with an axial bore or aperture 8 tapered inwardly as shown. The dimensions of the unit parts may, of course, be varied to best suit the demands of specific uses, but I have found it practical to employ a shell eight and seven-eighths inches long, with an inside diameter of one and one-half inches and an outside diameter of one and seven-eighths inches. In such a unit the plug aperture preferably is provided with an outside diameter of one-half inch and an inward taper of about ten degrees, so as to form a guideway to facilitate insertion of the end of a conductor wire and an actual bare wire receiving opening just large enough to permit insertion of one bared conductor wire end as shown in Figure 1 of the drawing.

At its other end, the shell 5 is internally threaded, as at 9-, to receive the reduced and threaded end ll] of a wooden closure plug l l equipped with an axial aperture l2 constructed like the plug aperture 8 previously described. The outer face of the screw plug is provided with a recess 13 disposed adjacent the periphery so as to align with the thread circle, and a longitudinal bore H extends through the shell, entering through the recess l3 and extending through the threaded periphery of the threaded portion Ill. The bore l4 constitutes a thread lock keyway and preferably is formed while the plug is mounted in the receiving end of the casing 5 so that the completed bore extends through the thread circle, half in the periphery of the plug extension I and half in the inner face of the casing as shown in Figures 1, 3 and 4.

When the parts are assembled a lock pin [5 is inserted into the bore [4 and locks the screw plug H against removal. After the pin has been inserted a suitable sealing substance is applied to the recess l3 concealing the pin and serving as a means for rendering improbable undetected, unauthorized tampering with the unit.

The unit preferably is rendered impervious to moisture by an internal 'paraffin coating l6 and an outer protective stain coating I1.

A contact plate l8, preferably of brass, abuts the end. plug 6, closing over the aperture 8 therein, and a coil spring IQ of suitable electricity conducting material engages the plate and serves to hold the plurality of dry cell battery units 20 in engagement with each other and with the closure plug extension It], as shown in Figure 1. Three battery units are shown cooperatively assembled in Figure l of the drawing, but it is to be understood that the unit may be designed to enclose a greater or lesser number of such units.

The improved blasting unit, assembled as shown in Figure l, and safely sealed against tampering, is adapted to convenient completion of blast charge firing circuits as diagrammatically indicated in Figure 1, without provision of any exposed or outside terminals to which operatives can carelessly make permanent conductor wire connections. In the use of the unit an operative inserts a bared end of each of the conductor wires 2 I, 22 leading from the prepared blast charge into one of the end apertures 8, l2, one thereof making mere touch contact with the plate I I 8 and the other with the positive terminal of the battery unit opposed to the aperture l2. The apertures 8 and I2 are flared enough to facilitate insertion of the wires into contact making position, but at their restricted ends are so small that any attempts to improperly insert two wires into one aperture, out of ignorance or with the intent to effect a multiple shooting, must meet with frustration.

Unless the wire ends are held in the apertures 8,. I2 by the operative, thus completing the blast circuit and firing the charge, they immediately fall out and break the circuit. Thus, it is impossible for an operative to make and maintain contacts at the unit, and, upon failure of the blast charge to fire, to go along the line seeking broken wires with the possibility of accidently or otherwise engaging the broken wires with disastrous results.

In Figures '7 and 8 of the drawing I have illustrated a modified lock pin mounting. Instead of boring the lock pin receiving hole across the threads longitudinally of the unit, as shown in Figures 1 and 3, a hole 23 may be drilled. across the threads transversely and at an angle so as to avoid the end opening l2 as shown in Figures 7 and 8. At the outer end, where it passes through the casing end, the hole may be enlarged, as at 24, to receive the head 25 0f the locking pin 26 and a suitable sealing substance 21 such as sealing Wax.

The improved blasting unit herein disclosed will be recognized as capable of being very cheaply manufactured, and it is efficient and safe in use, is subject to long life because of its simple, compact and sturdy construction and because it can be conveniently refilled, and is proof against unauthorized tampering.

What I claim is:

A device of the character described comprising a hollow cylindrical shell, an axially apertured plug closing each end of the shell, battery elements encased within the shell and presenting a positive terminal toward one plug aperture and (,3

a negative terminal toward the other aperture, a contact plate opposed to one aperture, and a contact spring interposed between the plate and the opposed battery terminal and serving to hold the plate and the battery contact at the opposite end,,

of the shell against the apertures which they oppose, said plug apertures being very small at their ends entering the shell and outwardly flared so as to pass the bared end of an insulated wire but only partially receive and obstruct passage (3 of an insulated portion of said wire, one said plug being threadably received in said shell, said shell having a surface recess at the position of said threadably received plug, a securing pin entering the shell and plug across the threads thereof,

through said recess and at an angle to the axis of the shell, and sealing means for closing said recess.

GEO. o. NELMS. 

